ORIGIN OF THE RENAL ARTERY 



191 



.4 



B 



D 



Fig. 6 Profile drawings of embryos to show the difference in the curvature 

 of the rump region. A, man, 8.0 mm., H.E.C. No. 817; B, pig, 9.0 mm., H.E.C. 

 No. .52: C, rabbit, G.fi mm., H.E.C. No. 460; D, cat, 9.7 mm.. H.E.C. No. 446. 



rectly dorsal, instead of lateral or dorso-lateral, from the aorta. 

 In this case the dorsal portion of the periaortic net will be dis- 

 torted and obliterated, as was the ventral portion in animals 

 with a large Wolffian body, and in the cat and the rabbit the 

 dorsal segmental arteries may be expected to take no part in the 

 development of the renal or suprarenal arteries (see diagram, 

 fig. 7). 



7 



.^° 





Fig. 7 Diagram to show, A, roots from the aorta between the dorsal seg- 

 mental, mesonephric, and mesenteric arteries, and the periaortic plexus; B, 

 result of large Wolffian body, carrying forward the mesonephric arteries; C, 

 result of greater curvature of back, lengthening the dorsal arteries. In both 

 oases lateral branches enlarge to supplv the fields left vacant. 



It will be noted that the rabbit is mentioned in both of these 

 classes, and should therefore be restricted to a lateral origin of 

 these arteries, unconnected with either mesonephric or dorsal 

 segmental vessels; anomalies should be very rare. Sheep and 



